In Bangladesh, bats, humans, and livestock live in close proximity, with likely overlap in consumption of common food resources (e.g., date palm sap and various fruits). Pteropus bats in Bangladesh are reservoir hosts for Nipah virus, which is transmitted from bats to people through shared consumption of date palm sap and then can be transmitted from person-to-person. Given that Nipah virus is a pathogen with pandemic potential, increased understanding of potential transmission routes is highly valuable to design prevention strategies, such as reducing opportunities for human consumption of bat contaminated fruits and date palm sap.
Begin by examining the villages included in the study. All villages have community survey information, but only villages with active date palm sap collection had camera traps at date palm trees and only villages with bats feeding at fruit trees near human fruit consumption areas had camera traps at fruit trees.
Overall, 206 villages were included in the study: 60 case, 72 near control, and 74 far control villages were included. All had community surveys completed.
For villages with both trees observed:
Few visits to fruit trees, so focusing on date palm trees:
As stated above, 86 (out of 206) villages had active date palm sap collection and date palm trees were subsequently observed for bat visits.
On average 2 date palm trees were observed per village
Little variation between village types for the number of date palm trees observed per village
Most villages with date palm trees observed had at least one tree that received a bat visit (90%)
Stay and contamination percentages by village type
As stated above, 118 (out of 206) villages had fruit trees identified that were visited by bats located near the village and where animals/people consume dropped fruit, with fruit trees subsequently observed for bat visits.
For ease of data visualization and comparisons, any trees with 1 or 2 trees observed are grouped as other. Other = fig, indian olive, betel nut, cotton tree, jack fruit, papaya, rose apple, and tamarind.
## num_tree
## Min. :1.000
## 1st Qu.:1.000
## Median :2.000
## Mean :1.729
## 3rd Qu.:2.000
## Max. :3.000
Trees that received visits by buffet and village type:
As with date palm trees above, number of visits is a skewed reflection of the data as the same bat could be counted as multiple visits if entering and exiting the camera frame. Visit contamination durations are used.
For context, 57% of visits resulted in a contamination. Most visits to banana trees resulted in a contamination, while most visits to guava trees did not.
## [1] 206
## [1] 5056
## Village_ID participants_per_village
## Min. :1002 Min. :12.00
## 1st Qu.:1066 1st Qu.:25.00
## Median :2038 Median :25.00
## Mean :1985 Mean :24.54
## 3rd Qu.:3010 3rd Qu.:25.00
## Max. :3066 Max. :26.00
Fruit survey dataset includes 206 villages and 5056 respondents. Of the 206 villages, 60 are case villages, 74 are far control, and 72 are near control. Their were 1473 respondents in case villages, 1815 from far control villages, and 1768 from near control villages. The median number of respondents per villages is 25 (min-max: 12-26).
There are four main questions that assess fruit consumption by bari members, bats, and animals separated by tree type.
The following questions also provide information on the trees available for bats to consume:
| fruit | human_fruit | human_dropped_fruit | animal_dropped_fruit | bat_fruit | average |
|---|---|---|---|---|---|
| mango | 0.975 | 0.765 | 0.304 | 0.897 | 0.735 |
| buroi | 0.952 | 0.659 | 0.271 | 0.809 | 0.673 |
| guava | 0.941 | 0.466 | 0.207 | 0.839 | 0.613 |
| banana | 0.964 | 0.024 | 0.146 | 0.819 | 0.488 |
| lichhi | 0.904 | 0.188 | 0.081 | 0.686 | 0.465 |
| betel | 0.824 | 0.382 | 0.013 | 0.540 | 0.440 |
| jackfruit | 0.959 | 0.061 | 0.181 | 0.527 | 0.432 |
| blackberry.jam | 0.780 | 0.345 | 0.092 | 0.507 | 0.431 |
| papaya | 0.889 | 0.092 | 0.082 | 0.518 | 0.395 |
| star.fruit | 0.767 | 0.235 | 0.105 | 0.398 | 0.376 |
| palmyra | 0.725 | 0.270 | 0.055 | 0.408 | 0.365 |
| indian.olive | 0.790 | 0.241 | 0.068 | 0.335 | 0.359 |
| plum | 0.630 | 0.213 | 0.101 | 0.441 | 0.346 |
| date.palm | 0.614 | 0.214 | 0.077 | 0.438 | 0.336 |
| coconut | 0.880 | 0.170 | 0.004 | 0.068 | 0.281 |
| custard.apple | 0.575 | 0.078 | 0.053 | 0.410 | 0.279 |
| sofeda | 0.412 | 0.109 | 0.064 | 0.374 | 0.240 |
| watermelon | 0.840 | 0.006 | 0.046 | 0.044 | 0.234 |
| melon | 0.655 | 0.004 | 0.035 | 0.037 | 0.183 |
| river.ebony | 0.321 | 0.083 | 0.035 | 0.283 | 0.180 |
| elephant.apple | 0.442 | 0.077 | 0.036 | 0.138 | 0.173 |
| pomegranate | 0.496 | 0.040 | 0.019 | 0.120 | 0.169 |
| wood.apple | 0.388 | 0.063 | 0.009 | 0.042 | 0.125 |
| monkey.jack | 0.217 | 0.057 | 0.022 | 0.168 | 0.116 |
| rose.apple | 0.257 | 0.042 | 0.012 | 0.140 | 0.113 |
| latkan | 0.219 | 0.049 | 0.024 | 0.113 | 0.101 |
| wild.dates | 0.145 | 0.062 | 0.018 | 0.167 | 0.098 |
| cashew.fruit | 0.169 | 0.027 | 0.004 | 0.071 | 0.068 |
| water.chestnut | 0.164 | 0.005 | 0.003 | 0.014 | 0.046 |
| rattan | 0.057 | 0.006 | 0.002 | 0.023 | 0.022 |
| uriam | 0.016 | 0.002 | 0.002 | 0.016 | 0.009 |
Table of reported overall consumption by village type and tree type for the above questions:
Do any fruit trees grow in or around your bari?
How many [insert fruit] trees grow in or around your bari?
Do members of your bari eat any [insert fruit] off the ground?
Do members of your bari eat any [insert fruit]?
Do domestic mammals (cow,sheep,goat,pig,dog,cat) eat [insert fruit] off ground?
Do bats eat any [insert fruit]?
Reported consumption of dropped fruits by bari members was highest for mango (76%), buroi (66%), guava (47%), and betel (38%). Consumption was lowest for melon (0%), water chestnut (0%), and uriam (0%). While reported dropped fruit consumption of date palm fruit was comparatively lower, at (21%), dropped date palm fruit consumption was highest among case villages by the largest difference of any fruit. Case village consumption of date palm fruit was reported to be 29%, control near 21%, and control far 16%. The average reported consumption among all fruits was 16%.
Reported consumption of fruits by bari members among fruit tree types was generally high (mean = 57%) with little difference in consumption between village types. Fruits consumed the most were mango (98%), jackfruit (96%), banana (96%), buroi (95%), and guava (94%). However, date palm fruit consumption was again highest among case villages by the largest difference of any fruit. Case village consumption of date palm fruit was reported to be 71%, control near 62%, and control far 52%.
Reported consumption of dropped fruits by domestic animals was much lower than human consumption (mean = 7%). Dropped fruit consumption was highest for mango (30%), buroi (27%), guava (21%), jackfruit (18%), and banana (15%). Date palm fruit consumption was 8% overall; 7% in case villages, 6% in near control villages, and 10% in far control villages. Difference in consumption between village types overall seems to vary more among domestic animals than humans, though this may be due to decreased accuracy in observations of animal fruit consumption compared to human fruit consumption.
Reported consumption of fruits by bats was on average 33%. This was highest for mango (90%), guava (84%), buroi (81%), and banana (82%). In each case consumption was slightly higher in case villages compared to near control villages, and higher in near control villages than far control villages. Date palm fruit consumption was 44% overall; 52% in case villages, 40% in near control villages, and 40% in far control villages.
Date palm fruit consumption was highest in case villages for bat fruit consumption, human fruit consumption, and human dropped fruit consumption. Dropped fruit consumption is a proxy for consumption of fruits that may have been bitten or contaminated by bats. However, the high reported consumption of mango, guava, and buroi by bats compared with high dropped fruit consumption of these fruits by humans and animals is potentially notable.
Of the tree types included on the survey, only 6 had visits recorded using camera traps.
When examining bat fruit consumption more closely, for the 6 tree types that received bat visits, there is some mild difference in village types.
# plot bat fruit consumption with x-axis ranked by the average
rank_b_fruit_grouped_mean %>%
filter(fruit == "banana" | fruit == "date.palm"| fruit == "star.fruit"| fruit == "sofeda" | fruit == "guava" | fruit == "buroi") %>%
ggplot(aes(x = fruit, y = bat_fruit, color = case_control_group)) +
geom_jitter(height = 0, width = 0.2, alpha = 0.8) +
labs(x = "Fruit type",
y = "Proportion of baris with bats\nconsuming fruit",
title = "Proportion of respondants reporting bat consumption\nof fruits by village type") +
theme_bw() +
theme(axis.text.x = element_text(angle = 45, hjust = 1),
axis.title.y = element_text(vjust = 1)) +
scale_color_manual(
name = "Village type",
values = c(
"case" = "#E69F00",
"control, far" = "#56B4E9",
"control, near" = "#009E73"
)
)
There are several survey questions that provide additional insight into fruit consumption of humans, bats, and animals.
Human fruit consumption questions:
| case_control_group | median_household | mean_household | count | numNA | response_rate | sum_1 | prop_1 | sum_2 | prop_2 | sum_3 | prop_3 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| case | 3 | 2.736 | 546 | 927 | 0.371 | 53 | 0.097 | 38 | 0.070 | 455 | 0.833 |
| control, far | 3 | 2.735 | 950 | 865 | 0.523 | 98 | 0.103 | 56 | 0.059 | 796 | 0.838 |
| control, near | 3 | 2.694 | 886 | 882 | 0.501 | 109 | 0.123 | 53 | 0.060 | 724 | 0.817 |
Reported dropped fruit consumption by bari members was lowest in case villages, at 42%, compared to both categories of control villages. Of those who reported dropped fruit consumption, most stated only occasional consumption.
Domestic animals fruit consumption questions:
| case_control_group | count | numNA | response_rate | sum_households | proportion_households |
|---|---|---|---|---|---|
| case | 1298 | 175 | 0.881 | 290 | 0.223 |
| control, far | 1431 | 384 | 0.788 | 497 | 0.347 |
| control, near | 1539 | 229 | 0.870 | 473 | 0.307 |
| case_control_group | count | numNA | response_rate | sum_households | proportion_households |
|---|---|---|---|---|---|
| case | 1298 | 175 | 0.881 | 189 | 0.146 |
| control, far | 1431 | 384 | 0.788 | 289 | 0.202 |
| control, near | 1539 | 229 | 0.870 | 364 | 0.237 |
## <labelled<double>[4]>: How often do you feed bat or bird bitten fruit to your domestic animals?
## [1] NA 2 3 1
##
## Labels:
## value label
## 1 Most days
## 2 Once or twice a week
## 3 Only occasionally
| case_control_group | median_household | mean_household | count | numNA | response_rate | sum_1 | prop_1 | sum_2 | prop_2 | sum_3 | prop_3 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| case | 3 | 2.725 | 189 | 1284 | 0.128 | 19 | 0.101 | 14 | 0.074 | 156 | 0.825 |
| control, far | 3 | 2.830 | 289 | 1526 | 0.159 | 14 | 0.048 | 21 | 0.073 | 254 | 0.879 |
| control, near | 3 | 2.734 | 364 | 1404 | 0.206 | 37 | 0.102 | 23 | 0.063 | 304 | 0.835 |
| case_control_group | count | numNA | response_rate | sum_households | proportion_households |
|---|---|---|---|---|---|
| case | 58 | 1415 | 0.039 | 13 | 0.224 |
| control, far | 99 | 1716 | 0.055 | 7 | 0.071 |
| control, near | 49 | 1719 | 0.028 | 14 | 0.286 |
| case_control_group | count | numNA | response_rate | sum_households | proportion_households |
|---|---|---|---|---|---|
| case | 27 | 1446 | 0.018 | 9 | 0.333 |
| control, far | 31 | 1784 | 0.017 | 8 | 0.258 |
| control, near | 18 | 1750 | 0.010 | 9 | 0.500 |
| case_control_group | median_household | mean_household | count | numNA | response_rate | sum_1 | prop_1 | sum_2 | prop_2 | sum_3 | prop_3 | sum_4 | prop_4 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| case | 2 | 2.222 | 9 | 1464 | 0.006 | 3 | 0.333 | 3 | 0.333 | 1 | 0.111 | 2 | 0.222 |
| control, far | 2 | 2.375 | 8 | 1807 | 0.004 | 0 | 0.000 | 6 | 0.750 | 1 | 0.125 | 1 | 0.125 |
| control, near | 3 | 2.778 | 9 | 1759 | 0.005 | 0 | 0.000 | 4 | 0.444 | 3 | 0.333 | 2 | 0.222 |
| case_control_group | count | numNA | response_rate | sum_households | proportion_households |
|---|---|---|---|---|---|
| case | 1471 | 2 | 0.999 | 224 | 0.152 |
| control, far | 1814 | 1 | 0.999 | 259 | 0.143 |
| control, near | 1768 | 0 | 1.000 | 197 | 0.111 |
Consumption of fruits on the ground by animals 30%, and is lowest in case villages at 22%. Feeding bat or bird bitten fruits to domestic animals is less common (20%), but is again lowest in case villages at 15%. Among those who reported feeding these to domestic animals the behavior was reported to be most often done only occasionally in all village types.
Interestingly, more respondents reported that raw date palm sap and dirty sap is fed to domestic animals in near control villages compared to far control or case villages. However, in far control and case villages date palm sap is fed to animals most often daily compared to about once per week in near control villages.
An important thing to note, however, is that response rate for some
of these questions is much lower than the questions about fruit trees.
For example, question q3_12 about feeding sap to animals
had a response rate of only 0.44%.
Bat fruit consumption questions:
| case_control_group | count | numNA | response_rate | sum_households | proportion_households |
|---|---|---|---|---|---|
| case | 1470 | 3 | 0.998 | 1298 | 0.883 |
| control, far | 1810 | 5 | 0.997 | 1431 | 0.791 |
| control, near | 1767 | 1 | 0.999 | 1540 | 0.872 |
| case_control_group | count | numNA | response_rate | sum_households | proportion_households |
|---|---|---|---|---|---|
| case | 1298 | 175 | 0.881 | 928 | 0.715 |
| control, far | 1431 | 384 | 0.788 | 733 | 0.512 |
| control, near | 1540 | 228 | 0.871 | 902 | 0.586 |
| case_control_group | count | numNA | response_rate | sum_households | proportion_households |
|---|---|---|---|---|---|
| case | 1470 | 3 | 0.998 | 631 | 0.429 |
| control, far | 1805 | 10 | 0.994 | 954 | 0.529 |
| control, near | 1767 | 1 | 0.999 | 923 | 0.522 |
| group | mean_household | count | numNA | response_rate | sum_1 | prop_1 | sum_2 | prop_2 | sum_3 | prop_3 | sum_4 | prop_4 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 67.651 | 923 | 845 | 0.522 | 156 | 0.169 | 51 | 0.055 | 380 | 0.412 | 276 | 0.299 |
| 2 | 207.295 | 954 | 861 | 0.526 | 189 | 0.198 | 60 | 0.063 | 390 | 0.409 | 119 | 0.125 |
| 3 | 24.843 | 631 | 842 | 0.428 | 124 | 0.197 | 67 | 0.106 | 272 | 0.431 | 154 | 0.244 |
Villagers report commonly seeing dropped fruits that have been bitten by bats or birds. This is highest in case villages at 88%, followed by near controls at 87%, and far controls at 79%.
Of those who reported that they see fruits on the ground that have been bitten by bats or birds, about 60% reported that it occurs during this time of year (winter). This was highest in case villages, at 71%, followed by near controls at 58% and far controls at 51%.
Case villagers reported seeing fruit bats in their trees at night the least, at 43%, compared to control villages, both at 52%.
Number of trees in bari (q5_frt#_5_2)
Animal ownership (q4_#_1)